Present day HVAC ducts suffer from a number of disadvantages. First, sections of duct are not easily connected one to another generally requiring the installation of as many as 8 screws around the periphery of the joined ducts at each joint. This is laborious and time consuming. Second, it is a problem to cut a section to a particular length, whether the duct section is rectangular or round, the duct must be measured and then a circumferential line drawn at the length desired so the tin snips have a guide to follow. Third, the cut edges are sharp and pose a significant risk to anyone handling the cut duct.
Fourth, most HVAC ducts experience significant amounts of leakage at the joints resulting in pressure drops at the vents. One conventional means of reducing leakage at the joints is to increase the lengths of the duct, thereby reducing the number of joints. This makes handling the duct more difficult. Another means to cope with leakage is to tape the joints using a tape and/or messy mastic. Fifth, most HVAC ducts are difficult to suspend or mount between joists since they lack any integral connecting means. Sixth, most ducts are made of sheet metal. It is estimated that losses in heating efficiency can be as high as 60% due to convective and radiative heating of the typically uninsulated air space surrounding the duct. Sheet metal ducts also pose a significant hazard to handlers, particularly when a burred or sharp edge has been created due to cutting to length.
Finally, in new construction, the use of floor-mounted boots can often cause problems since any dust and debris can fall into the grate and remain lodged in the duct. When the furnace is activated, the dust and small debris particles become airborne which becomes a nuisance to the home owner and frequently results in a service call for the HVAC supplier to identify the source of the objectionable odor.
It is among the objects of the present invention to overcome the deficiencies of the prior art HVAC ducts. The HVAC duct of the present invention is equipped with a quick connector for adjacent sections. This connector has opposing cylindrical surfaces equipped with inwardly protruding fingers which form a "chinese finger puzzle" gripper which can engage an end of another section of duct. Preferably, a separate connector may be equipped with two grippers, one on either end, to interconnect two sections of duct. Alternatively, each section of duct may have a connector integrally formed on a first end of the duct for engagement of an opposing end of the adjacent duct section.
The entire length of the duct of the present invention may have spaced there along at equal distances a series of peripheral ribs. These ribs serve to provide structural rigidity as well as enable cutting to particular length. The ribs provide a guide to the shears to enable more precise circumferential cutting to length. In addition, at least two circumferential ribs are engaged by the gripping fingers to ensure interconnection of the duct sections. Alternatively, indicia may be provided on the surface of the duct to provide the ready measurement feature if the gripping fingers provide adequate retention force without the ribs. Each recess is lined with a layer of insulative foam, such as foam rubber, or other insulative material, so that the received end of the duct seals in the material. The insulative foam results in retention of as much as 90% of the pressure at the duct inlet arriving at the outlet.
Each duct section is equipped with two eared circumferential bands which permit easy securement between floor or wall joists. The duct system of the present invention further includes a floor-mounted elbow boot which is equipped with a removable plastic cover which permits the duct to be protected from dirt, dust and debris settling into the vent before construction is complete.
While the duct of the present invention can be made of sheet metal, it is most preferably manufactured of plastic. Plastic is not as aggressive a conductor of heat as metal and hence, does not rob the system of as much heat through conductive, convective and radiative heat losses. Further, the cut edge of the plastic duct does not pose as significant a threat to its handler as the sheet metal duct.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.